This application relates to belt retractors of the type in which a reel is normally spring biased in a direction tending to wind a belt around the reel. Such retractors are presently being widely used in connection with automobile seat belts. The present invention particularly relates to belt retractors of the so-called "tensionless" type which are designed to be placed in a condition in which retraction of the belt is blocked.
Many well known types of automobile seat belt systems employ belt retractors in which torsion springs continually bias the reel in a direction tending to wind the belt around the reel. These types of retractors are desirable because when the seat belt is unbuckled and released the belt is automatically wound about the reel. The belt remains in the wound condition until it is protracted and buckled about a wearer. When the belt has been extended about the wearer and buckled the belt is continually biased into a snug fit about the wearer.
Experience has shown, however, that many people object to continually feeling the rewind force exerted on the belt, and such people may be reluctant to make use of such a seat belt. Therefore, various types of mechanisms have been designed for placing the seat belt system in a "tensionless" condition, a condition in which the rewinding of the belt under the bias of the spring is resisted. Many people find this a more comfortable type of seat belt since they are not constantly subjected to the rewind force exerted on the belt. Consequently, such people are more likely to make use of seat belts having this feature.
One type of tensionless retractor is shown in U.S. Pat. No. 3,851,836. In this patent a control disc is frictionally clutched to the reel. The control disc includes recesses which cooperate with a locking pawl and allow the locking pawl to engage ratchet teeth on the reel to lock the reel against rewinding. Also included in this reference are a pair of surfaces on the control disc which serve to engage the pawl and maintain the locking pawl out of engagement with the ratchet teeth. According to this disclosure the reel, after initial protraction, is in one of two conditions; (1) a condition in which during the initial retraction the locking pawl automatically engages the ratchet teeth and locks the reel against further retraction, or (2) a condition in which after the belt has been retracted to a snug position about the wearer the belt must be slightly protracted and then allowed to retract in order to allow the locking pawl to engage the ratchet teeth and place the belt in a tensionless condition. Which condition the system is in depends solely on the rotational position of the surfaces when the belt is protracted to the desired length.
Another form of tensionless retractor is shown in U.S. Pat. No. 3,869,098. In this patent a pair of discs are provided, a first one of which is frictionally clutched to the reel, and the other of which is frictionally clutched to the first disc. These discs have fixed surfaces which cooperate with a locking pawl in a predetermined manner and are adapted for a predetermined amount of rotational movement relative to the reel and to each other so that a tensionless condition is reached only after the belt has been protracted, allowed to retract, then protracted very slightly, and then allowed to retract. U.S. Pat. No. 3,834,646 also discloses a pair of discs which cooperate with a locking pawl in a similar manner to place a retractor in a tensionless condition.
Another form of tensionless seat belt retractor is shown in U.S. Pat. No. 3,206,137. One or more pawls are pivotally mounted on the reel. A fixed locking member having a plurality of teeth is provided, and the pawls are biased into engagement with the teeth of the fixed locking member. The pawls ratchet over the teeth, and during initial retraction of the belt serve to engage appropriate teeth of the locking member to lock the reel against rewinding. In this patent, and in the aforementioned patents, the belt can be released from a tensionless condition and allowed to rewind under the influence of its rewind spring by simply protracting the belt further outwardly from its tensionless condition and then releasing the belt.
Another form of tensionless retractor is shown in U.S. Pat. No. 3,682,412. In this patent a stop is manually actuated to prevent retraction once the belt is pulled out to the desired length. To permit the belt to retract under the influence of its return spring this device is adapted to be manually deactivated.
Still other types of prior art retractors relate to machanisms which are designed so that when a locking element is in a predetermined condition it prevents both retraction and protraction. Many of these require manual release of the locking element to allow the retractor to rewind under its spring bias.